Carbohydrate-protein interactions are essential for a wide range of biological processes such as inflammation, bacterial and viral adhesion, and metastasis. As a result, there has been significant interest in identifying carbohydrate binding proteins and developing ligands to modulate their activity. Analysis of carbohydrate-protein interactions is complicated by a number of factors. First, carbohydrates are extremely difficult to isolate or synthesize. Therefore, only small amounts can be obtained in many cases. Second, traditional methods for studying binding are not high-throughput and require large amounts of material. Third, monovalent interactions between carbohydrates and proteins are notoriously weak. To achieve a high avidity, carbohydrate-binding proteins contain multiple binding sites and form multivalent complexes. As a result, carbohydrates must be presented in a multivalent fashion and the spacing and orientation of the carbohydrates play a critical role in recognition. Carbohydrate microarrays contain many different carbohydrates immobilized on a solid support in a spatially-defined arrangement. Using an array, one can evaluate binding of a lectin, antibody, cell, or virus to all the carbohydrates on the array simultaneously. The array provides a multivalent presentation of carbohydrates, and the miniaturized format requires only picogram amounts of each carbohydrate for an assay. We have successfully generated a carbohydrate microarray and assay to detect binding. Our current generation microarray contains 128 different components. The array format is ideally suited to examine many combinations of both carbohydrate structure and carbohydrate density for recognition. We are continuing to expand and improve the array.